at home, to made in america, claiming a kind of victory tonight. The american powerhouse, apple, famous for its giant manufacturing operations in china, has proo do something they have not done in nearly 20 years. Build some apple computers right here in the united states. And abc's david muir, captain of our made in america team, is here with the latest. Reporter: Diane, as you know, for nearly three decades, apple made its computers in the u.S. Tonight, word one of those lines will bear those three words we've been talking so much about here. Made in america. Tonight, that bold announcement from apple. Ceo tim cook now says some of apple's mac computers will never year carryse three words, made in america. Cook telling bloomberg business week that the company plans to spend 1$100 millioner in year to move production fr mac line from china back here to the u.S. It was this year, when asked about the factories they used to have here in america that tim cook talked about the possibility of bringing manufacturing back. There is some manufacturing revival in the u.S. Will there be an apple product ever made again in the united states? I want there to be. Reporter: And now a promise that there will be. The vast majority of apple products are made overseas. Wow. Reporter: The factories in china made 40% of the world's electronics. Where just this year, abc's bill weir took you inside for an exclusive look, after working conditions there came under fire. This new move by apple, moving their line of macs back to america, still represents a small percentage of apple's overyou a product line. Iphones, ipads sti assembled overseas. But cook has made the point before that key components for the iphone are made in america. The processor, the glass in kentucky. Will it ever say on the back of a product, made in the united states? Several parts are from the united states. Reporter: Apple is now joining a trend that we reported on extensively here on "world news." An early wave of american wo companies rethinking where they make their products. Chinese wages have come back. And another reason to come back, location. Make it here and you don't have to ship from china, saving a lot of money. Suddenly, the math isn't adding up. So, they are decides that made in america makes more sense. Yes, it's an economic question about being made in america. It's not necessarily a patriotic question. It's an economic question. Reporter: One that also creates a ripple effect here at home. The other jobs created. Just last night, we introduced you to arianna russell in st. Louis, making her own iphone cases and determined to make her design here in america. So, you found a way to do it here. I found a way to do it here. Reporter: There was so much interest in those cases last night that her website crashed within five minutes of our report. But it's back up and running tonight and she tells us she sold 2,000 of the cases in 24 hours. On this larger announce m from apple tonight, we reached out to our team of economists and they all echoed one another, saying this is about more than just good will. It's now good business. And this move puts an exclamation point on the trend we've all been reporting here. American jobs, back on the case again tonight. Thank you, david.

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